P2-1 Jitter Simulation in High Resolution Digital Audio—Malcolm Hawksford, University of Essex - Colchester, Essex, UKTo reconstruct an audio waveform samples must be located precisely in time. Practical systems have sources of jitter described by both correlated and uncorrelated elements that result in low-level distortion. However, less well known is how different forms of jitter distort an audio signal. Jitter theory is developed to produce a simulator to enable jitter-induced distortion to be determined. Distortion spectra can then be observed and time domain distortion auditioned. Jitter induced distortion is compared to a range of errors, including DAC errors and incorrect use of dither. System architectures studied include LPCM with up-sampling and noise shaping and SDM.Convention Paper 6864 (Purchase now)

P2-2 The Performance of Look-Ahead Delta-Sigma Modulators with Unstable Noise Shaping Filters—Steve Hoare, Jamie Angus, University of Salford - Salford, UKLook-ahead sigma-delta modulators look forward k samples before deciding to output a “one” or a “zero.” We look at the performance of such modulators, when used with unstable noise shaping filters, and examine the trade-off between the number of paths that must be kept alive and the look-ahead depth needed to assure stability. Such information helps define the number of required paths in a “Pruned Tree” algorithm or the stack size in a “Stack” algorithm, as well as the minimum search depth required. Results are presented showing that an unstable noise-shaping filter, with an out-of-band gain of 3.0, can be used successfully. This gives a 10 to12 dB improvement in signal-to-noise ratio, compared to a conventional modulator.Convention Paper 6865 (Purchase now)

P2-3 Prediction and Verification of Powered Loudspeaker Requirements for an Assisted Reverberation System—Mark Poletti, Industrial Research Limited - Lower Hutt, Wellington, New Zealand; Roger Schwenke, Meyer Sound Laboratories - Berkeley, CA, USAElectronic enhancement systems are being increasingly used to provide control of the acoustics of multipurpose venues. Reverberation enhancement systems are an important component of such systems. These provide an electroacoustic field that supports the naturally occurring reverberant field using multiple microphones and loudspeakers. This paper derives a simple formula for the on-axis SPL required to support a given sound field. The formula is verified by measurements in two rooms with installed assisted reverberation systems. A relative measurement method is also developed to allow the maximum level to be determined from measurements at a lower level.Convention Paper 6866 (Purchase now)

P2-4 The Representation of and Control Over Mixing Desks via a Software-Based Matrix—Richard Foss, Philip Foulkes, Rhodes University - Grahamstown, South AfricaThe control over all the parameters of a mixing desk can be a daunting task. This paper describes a software system that has been created to represent the signal processing and routing functions of MIDI-controllable mixing desks in a conceptually clear manner. Input to output routings are displayed in the form of a matrix, while signal processing functionality can be accessed at the inputs, outputs, and cross-points. XML is used to capture the elements of the mixing desk and to associate appropriate MIDI control messages with these elements. This enables the same matrix template to be used for many mixing desks. Remote control is enabled by IP-based MIDI routing software known as MIDINet.Convention Paper 6867 (Purchase now)

P2-5 A Cascaded Delta Sigma DAC with DWA Decreasing Mismatch Effect—Yousuke Terada, Akira Yasuda, Masao Zen, Syunsuke Katsumi, Hosei University - Tokyo, JapanIn this paper we propose a small-sized and high-performance cascaded delta-sigma DAC (CDS-DAC) that uses an analog FIR filter including second mismatch shaping functions. If a multibit DAC was composed, the mismatch caused by a variation of elements degrades the overall performance of the analog part. We propose a novel CDS-DAC having a second-order mismatch shaping function, which can be realized with several switches in the analog part and a first order mismatch shaper in the digital part in order to improve a performance degradation caused by the mismatches. The simulation shows that the SNR of the proposed CDS-DAC is 122 dB where the oversampling ratio is 128 and the mismatch of components is 1 percent.Convention Paper 6868 (Purchase now)